1858.] NICOL EASDALE AND OBAN. 115 



green on the fresh fracture, but becomes reddish or greenish brown 

 on exposure to the weather. The sides of the vein, for about an 

 inch deep, are compact; but the centre is made up of rounded 

 concretions, about the size of peas, separated by cavities with rough 

 drusj surfaces. The more common veins run nearly at right angles 

 to these and to the cleavage-planes, or from N.W. to S.E. (N. 53° W. 

 to S. 53° E.). In mineral character they are generally fine-grained 

 dark- coloured greenstones or dolerites, but are often porphyritic or 

 amygdaloidal. They vary, even in Easdale, from a few inches to 

 several yards in thickness, and in this and other respects show many 

 interesting irregularities. Thus, some of them divide and ramify in 

 most singular forms ; another will thin out and disappear, but a 

 similar vein, commencing a few yards to the side, and gradually 

 increasing, forms, as it were, its continuation. One vein, 24 feet 

 wide, of dark-grey greenstone was in one place cut off abruptly 

 by the slate, and shifted 16 feet to one side. Some of the veins 

 enclose fragments of slate, often of considerable size. In these 

 pieces the cleavage is quite distinct, but lying in different directions, 

 so that this condition must have been impressed on the slates before 

 the intrusion of the veins. Where these trap-veins are of small 

 dimensions, they do not seem to have greatly affected the slates ; 

 but where they are thicker, the slate is in some places more friable, 

 in others hardened or converted into a kind of flinty slate. 



Pitchstone-vein. — Another remarkable vein is seen on Seil, near 

 the old Danish Fort. The main vein consists of greenstone ; but it is 

 accompanied, sometimes on one side, sometimes on both, by a thin 

 layer of pitchstone, from half an inch to one or two inches wide. 

 The greenstone-vein varies from one to three feet broad, but in one 

 place is six feet wide, and is there intersected |by the pitchstone- 

 veia, which also becomes wider. I traced these veins for more 

 than a quarter of a mile along the beach*. The pitchstone is very 

 dark-green or black, with a prismatic structure and conchoidal 

 fracture ; in small fragments it has much resemblance to glance - 

 coal, for which it might be mistaken. The occurrence of this 

 mineral in this place is interesting, as forming a connecting link 

 between that observed in Skye and Eigg and that of Arran and the 

 north of Ireland. 



Connexion and age of the Trap-veins. — The direction of the 

 second class of trap-veins in Easdale points directly to Mull, and 

 indeed to Ben More, the loftiest of the igneous mountains in that 

 island. It might thus be supposed that they were connected 

 with this focus of igneous activity. However, we find similar 

 veins, and nearly parallel in direction (jST.W. or N. 48° W.), both 

 in other parts of Seil and on the Sound of Kerrera, near Oban, 

 and thus with no tendency to converge to a centre. Besides, on the 

 coast of Mull, between Duart Castle and Craiganure, I have 

 observed two sets of veins running nearly parallel to those in 



* In July 1858 I found the continuation of these veins in the small bay north 

 of the village ; and fragments of a similar pitchstone on the hiUs near Oban. — 

 J. N., Januarv 1859. 



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